Endless conveyors are used in many industries to move articles. In industries such as the glass industry such conveyors are employed to carry fiberglass material, for example, fiberglass bats of building insulation, through high temperature ovens during its manufacture. Typically, such ovens employ conveyors driven by endless chains of conventional design which themselves pass through the high temperatures of the ovens.
The chains which drive the conveyors are well known. They are made up of a plurality of links which are each formed of a pair of parallel link plates joined at each end by a cylindrical rollers, which engage the notches of sprocket wheels that drive or are driven by the chains. Adjacent links are pivotally joined at the rollers. Each roller typically has a link pin at its axis surrounded by an annular bushing. The pins have a head at one end and a lock pin at the other to hold the adjacent links together.
Conveyor chains of this common type require continuous lubrication to prevent the wear of the contacting surfaces between the pins, the bushings and the rollers. With many uses of conventional chains, the occasional application of lubricant to the chain is sufficient, and application of the lubricant to the entire chain, including pins, bushings, collars and links, is common. Normally, petroleum based lubricating oils are adequate.
In high temperature applications such as are faced with the conveyor chains used in ovens such as those of the glass industry, ordinary lubrication methods have many disadvantages. In such applications, the conveyor chains are large, with approximately six inch links, and are, for example, fifty to two hundred feet in length. The chains operate continuously, and encounter constant temperatures of from 400 to 1000 degrees Fahrenheit. When such chains operate in this high temperature environment, ordinary oils will burn and lose their lubricating properties. This has required the use of specialty oils such as high temperature synthetic oils that can retain their lubricating properties in such high temperature environments.
High temperature synthetic lubricating oils are considerably more expensive than ordinary petroleum based lubricating oils, often over five times the price. Even these oils, when used in high temperature ovens, require constant reapplication, since even they will dissipate and leave the chain dry and unlubricated. Because of the size of the chains, when they are continuously and totally wetted with the lubricating oil, consumption of the oil is high, and significantly contributing to the overall manufacturing operation. Furthermore, as the oils encounter the heat of the ovens, vapors and smoke are generated in proportion to the amount of oil applied to the chains. The vapors and smoke that are produced must be exhausted away from the atmosphere and personnel within the manufacturing plant, and requires expensive air cleaning equipment to prevent the smoke and vapors from being released into the external atmosphere.
To solve some of the problems set forth above, it has been proposed to limit the amount of lubricant applied to the conveyor chains by selective application of the oil to only the pin and bushing assemblies of the chains. This has been done by intermittently dispensing discrete quantities of oil on the chain as it passes a lubrication station in an attempt to apply oil only at the junctures of the links. In doing so, prior art systems have met with only limited success.
The chains of conveyors that transport materials such as fiberglass through high temperature ovens move at fairly high speeds, of for example, up to 300 feet per minute. At 300 feet per minute, with chains of links that are six inches in length, 600 pins per minute, or 10 pins per second, pass any given lubrication station. In addition, in that the pins are approximately one 3/4th inch in diameter, they are adjacent the lubrication station little more than 1/100th of a second. This has made the application of the concept of applying lubricant only to the pins difficult to practice. In that the loss of lubrication can result in costly damage to the conveyor, or at least reduced chain life and higher power consumption, such systems of the prior art have had limited acceptance in the industry.
Efforts to time the dispensing of drops of lubricant and synchronize the application of the discrete amounts of lubricant with the pin positions have been proposed, such as in U.S. Pat. Nos. 3,869,023, 4,085,821, 4,271,930, 4,274,509 and 4,368,803 relating to one line of lubricators by the Madison/Kipp Corporation of Madison, Wis. These systems have switched the lubricating oil on and off at pump remote from the discharge point of the fluid onto the chain. With high speed conveyors such as are encountered in the glass industry, difficulty in switching the flow of lubricant on and off so as to keep up with the speed of the chain has resulted in either too much lubricant being applied, too little lubrication of the critical surfaces in contact with the link pin bushings, or both.
In U.S. Pat. Nos. 4,537,285 and 4,844,203, it has been proposed to lubricate only every one of a predetermined number of pins that pass the lubricant dispensing point. In theory, spacing the drops more widely should make it easier to trigger the initiation of the dispensing cycle, particularly where the system is otherwise slow to respond. However, the problem of precisely focusing of the dispensed fluid droplet onto the point of the chain at which it is needed is not solved by this concept.
DeLimon Fluhme & Co. of France has produced a shot valve, referred to as the DeLimon Lubricant Metering Element ZE-E, that dispenses a measured shot of lubricating fluid once every time fluid pressure is applied to valve inlet. This valve had been employed in a chain lubricating system once marketed by BiJur Corporation of Bennington, Vt. In the BiJur system, the valve was positioned adjacent the chain and intermittent application of lubricant to the valve was controlled at the pump located remotely at a lubricating fluid reservoir. The system attempted to apply lubricant to each consecutive pin of the chain, but could not effectively apply lubricant only to the pins of the chain with a chain that moved at high speed.
Accordingly, there still remains a need for a method and apparatus that will apply lubricant in economical but effective amounts on only the pin and bushing portions of a high speed conveyor chain such as are used in high temperature ovens in the manufacture of fiberglass. The systems of the prior art have been inadequate in filling this need.